Obviously, that's a frightening statistic, because cancer is a frightening disease. CRUK is keen to point out that this isn't a sudden leap in risk – it's down to a new and, it says, more accurate method of calculation. Our risk of cancer has been increasing steadily for decades.

I know that sounds callous, especially if you or a loved one have recently been diagnosed with cancer. How can it possibly be that the rise in a deadly disease is a good thing?

But cancer happens when our cells mutate as they divide, and the older you get – and the more times your cells divide – the more chances there are for something to go wrong. The main reason that more people are getting cancer is that more people are living to an age where they can get it.

Professor Peter Sasieni, the author of the CRUK study, says: “Cancer is primarily a disease of old age, with more than 60% of all cases diagnosed in people aged over 65. If people live long enough then most will get cancer at some point."

In short, the reason people are dying of cancer is that they're not dying of anything else first.

You can see this most starkly when you compare what kills people in the affluent West with what kills people in the developing world. According to the World Health Organisation, the top 10 causes of death in the West include four different cancers – stomach, lung, breast, and colorectal – but only one kind of contagious disease, lower respiratory tract infections.

In contrast, the top 10 killers in the developing world include no cancers at all, and five contagious diseases: respiratory tract infections, diarrhoeal diseases, tuberculosis, malaria, and HIV/AIDS. Tragically, millions of people in the developing world are not living long enough to develop cancer.

That isn't the whole story, but it's a large part of it.

CRUK estimates that two-thirds of the increased cancer risk is due to our improved life expectancy. The other factors are to do with our lifestyle. We can't stop ourselves getting older – and in fact we should be grateful that we get to do so – but, says CRUK in a blog, "we can stack the odds of avoiding cancer in our favour. Things that happen throughout our lives can speed up – or slow down – the rate at which errors occur in our genes. These include things we can control, and some we can't."

CRUK lists a few of the specific things that are behind the increased cancer incidence. Changing diets – an increase in the consumption of red and processed meat – seem to be behind the rise in bowel cancer rates. Obesity and excessive alcohol consumption increase the risk of several cancers. Sunbathing and sunbeds are behind a rise in melanoma risks. The fact that women are breastfeeding less and having babies later also appears to have contributed to a rise in breast cancer.

The big one is smoking, and that is a partial success story, as the above chart shows. Smoking rates have been dropping in the UK for years, leading to a drop in lung cancer rates – at least in men. But women's risk of lung cancer is still rising.

As well as lifestyle changes, medicine can help prevent cancers. There are various infections which raise your risk of cancer – for instance, the human papilloma virus (HPV) increases a woman's risk of cervical cancer. There is a vaccine for HPV which, if given to girls young enough, can dramatically reduce that risk. Other cancer-causing infections, such as the Epstein-Barr virus, don't yet have vaccines, but research is ongoing.

As well as changes to our lifestyles, there are other ways to help prevent cancer. “Certain drugs could be used to reduce the risk,” says Kat Arney, senior science information manager at CRUK. “Aspirin is a big one, but there are others being looked at too.”

“As well as preventing the disease, there needs to be a huge emphasis on early diagnosis to improve survival. It’s still very difficult to treat cancer that has spread through the body, so we need to find better ways to detect the disease early, when treatments are more likely to be successful.”

Even leaving aside the fact that the main reason we're getting cancer is because we're living longer, cancer is much less of a death sentence than it used to be. Your odds of surviving 10 years after a cancer diagnosis have doubled in the last four decades. That's partly because a lot of cancers are being diagnosed earlier, but also because of improved treatments.

The likelihood that a newborn child will get cancer at some stage in their lives is probably going to carry on going up. This latest news should remind politicians and health bosses that cancer is going to be one of the biggest health challenges of the coming decades – and a huge focus on research, diagnosis, and treatment, as well as support for patients and their families, is vital. But the bald statistic that half of us will get cancer, while scary, is actually heartening. We are getting cancer because we're not dying of anything else – and nowadays, a cancer diagnosis isn't the death sentence that it used to be.